1. Technical Field
The present invention relates to a zoom lens system, an imaging device and a camera. In particular, the present invention relates to: a zoom lens system that is used suitably in a small and high-image quality camera such as a digital still camera or a digital video camera, hence has high resolution, and has a blur compensation function of optically compensating blur caused in an image by hand blur, vibration or the like; an imaging device including this zoom lens system; and a thin compact camera employing this imaging device.
2. Description of the Background Art
With recent progress in the development of solid-state image sensors such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal-Oxide Semiconductor) having a high pixel, digital still cameras and digital video cameras are rapidly spreading that employ an imaging device including an imaging optical system of high optical performance corresponding to the above solid-state image sensors of a high pixel.
Among these, especially in digital still cameras, thin constructions have recently been proposed in order to achieve satisfactory accommodation property or portability to which the highest priority is imparted. As possible means for realizing such thin digital still cameras, a large number of zoom lens systems for bending a light beam as well as lens barrels and imaging devices employing these systems have been proposed.
For example, Japanese Laid-Open Patent Publication No. H11-258678 discloses a lens barrel comprising: a fixed first stage shooting lens; a plurality of movable shooting lens units arranged in the subsequent stages of the shooting lens; optical axis changing means in the middle of the plurality of movable shooting lens units; and driving means for moving in the shooting optical axis direction the movable shooting lenses located upstream and downstream the optical axis changing means. In this lens barrel disclosed in Japanese Laid-Open Patent Publication No. H11-258678, since the optical axis changing means is arranged in the middle of the plurality of movable shooting lens units, the interval is reduced between the shooting lens of the first stage and the movable shooting lens units of the subsequent stages. This reduces the diameter in the shooting lens of the first stage, and hence reduces the volume of the entire lens barrel.
Further, Japanese Laid-Open Patent Publication No. H11-196303 discloses an electronic imaging device comprising a shooting lens unit that has a plurality of lenses and optical axis changing means arranged between the plurality of lenses and that is arranged on the frontward of the photographic object side of an image display section provided in a rear face of a main body of the device, so that object light having passed through the shooting lens unit is photoelectrically converted and recorded by an image sensor. In this electronic imaging device disclosed in Japanese Laid-Open Patent Publication No. H11-196303, since the shooting lens unit is provided with the optical axis changing means arranged between the lenses, a construction is formed that the light beam is bent in the middle. Further, the image display section is arranged in the rear face. This avoids the main body of the device becomes thick, and realizes a shape of satisfactory balance where the horizontal dimension is reduced.
Furthermore, Japanese Laid-Open Patent Publication No. 2004-354869 discloses a zoom lens system that has a five-unit construction of positive, negative, positive, positive and negative in order from the object side, and that performs zooming by moving a second lens unit and a fourth lens unit, in which a first lens unit, in order from the object side, comprises a negative front side lens unit, an optical member for bending an optical path, and a positive rear side lens unit, and in which the imaging magnification of a fifth lens unit is set within a specific range. In this zoom lens system disclosed in Japanese Laid-Open Patent Publication No. 2004-354869, since the first lens unit comprises the negative front side lens unit, the optical member for bending the optical path, and the positive rear side lens unit, the moving direction of the second lens unit and the fourth lens unit at the time of zooming aligns with the optical axis direction of the rear side lens unit of the first lens unit. This reduces the thickness of the lens system. Further, since the imaging magnification of the fifth lens unit is larger than a specific value, the focal length is reduced in the lenses arranged on the object side thereof. This reduces the overall length of the lens system, and reduces the effective diameter in the front side lens unit and the rear side lens unit of the first lens unit.
Nevertheless, in the lens barrel disclosed in Japanese Laid-Open Patent Publication No. H11-258678, the shooting lens unit that moves in the optical axis direction in zooming is included between the shooting lens of the first stage located on the most object side and the optical axis changing means. Thus, the entire lens barrel is not sufficiently size-reduced. Further, the zoom lens system itself held by the lens barrel is not specified sufficiently, and hence this zoom lens system does not seem to correspond to blur compensation.
Similarly, in the electronic imaging device disclosed in Japanese Laid-Open Patent Publication No. H11-196303, the shooting lens unit itself is not specified sufficiently, and hence this electronic imaging device does not seem to have a sufficient blur compensation function. Further, the lens eyepiece part and the release switch are far apart from each other. This construction easily causes blur in the image owing to hand blur.
Further, in the zoom lens system disclosed in Japanese Laid-Open Patent Publication No. 2004-354869, a specific lens system having a five-unit construction is employed so that thickness reduction is achieved reliably while the overall length is reduced in the lens system. Nevertheless, its blur compensation function is not satisfactory, and has a problem that sufficient optical performance cannot be maintained when blur compensation is performed.